Recent CHIPS developments

1. Mikhail Kosov, 14th Geant4 Users and Collaboration Workshop, 2009 Recent CHIPS developments

2. Introduction The main goal of the CHIPS development is creation of a physics list, which is not using any other hadronic model (only CHIPS). The CHIPS package is already unique or the best for the following processes: At rest nuclear capture processes for negative (and neutral) hadrons Neutrino-nuclear, electron-, muon-, tau-nuclear and photo-nuclear reactions Elastic scattering for protons and neutrons Quasi-elastic scattering for the Geant4 QGS model New developments: On flight hadron-nuclear interactions Low energy 3-D CHIPS model (excitation and decay of Quasmons) High energy CHIPS string interaction interface extended to low energies Nuclear-nuclear interactions Fast (G4QLowEnergy) simulation appropriate only for low energies All-energies CHIPS ion-ion process (G4QInelastic – under development) CHIPS interaction cross-sections for hadron-nuclear and ion-ion interactions

3. Algorithm of the low energy CHIPS Simulation of the deep inelastic hadron-nuclear interactions is the same as in CHIPS stopping algorithm Nuclei are clusterized (nucleons are in di-baryon, tri-barion etc. states) The projectile hadron joins with one of the clusters and creates a Quasmon By quark-fusion or quark-exchange with other clusters energy is dissipated When the quark level algorithms are exhausted, switch to nuclear evaporation A few decoupled processes are added Quasi-elastic scattering of the projectile on nucleons and nuclear clusters G4QElastic process is used for this scattering on nucleons or on clusters Pick up process, which provides high energy forward nuclear fragments Final State Interaction of produced secondaries A kind of the nuclear fusion FSI reactions For energy and momentum correction in case of problems

4. CHIPS algorithm of the deep inelastic hadron-nuclear interaction t the created Quasmon the projectile hadron p d a NO RESCATTERING ! NO CASCADE, JUST A DECAY ! The example for 90 MeV protons on Al and Bi is following

15. New CHIPS string algorithm The 1-D CHIPS String is similar to the QG String, but… All partons are massless (current) instead of heavy (constituent, QGS) ones Thus the CHIPS string algorithm can work from E=0 (formally E>>mq) The hadron splitting in partons is made by the CHIPS algorithm: (1-x)N-2 If energy is restricted, the strings are fused or converted to hadrons Connection to the 3-D CHIPS algorithm In nuclear matter string looses (SEi) about k=1 GeV/fm ( DE=k*T(b)/r(0) ) This energy is converted to the Quasmon excitation The rest (high rapidity part of the string) is hadronized outside of the nucleus If at low energies the projectile energy is smaller than DE, string is skipped Special cases At low energies the transition to 3-D CHIPS can be used as an emergency Quasi-elastic on nucleons happens at all energies without the string excitation 0 1 N-1 random numbers

16. projectile hadron String algorithm p h p p h h p p h h 1-D (light cone) p p h h t p SEi p 3-D (Quasmon) DE d a

17. Problems in the string algorithm Because of the high transverse momenta of partons the resulting strings can have too low and even imaginary (tachionic) masses. There are a few steps in the CHIPS algorithm to avoid this problem: Try to fuse two or more strings with low masses Scatter on another string with high mass and convert to a GS hadron Scatter on the already produced hadron and convert to a GS hadron Fuse with the already produced hadron and increase the string mass Sometimes (at very low energies) the string reduction algorithm converges to elastic scattering, then the interaction is recalculated Be careful with the real threshold for inelastic interactions, as below the threshold the CHIPS algorithm can be looping (with the emergency stop) If the strings fusion algorithm fails to get rid of the low mass strings, the string 1-D algorithm is switched to the 3-D algorithm Otherwise the CLHEP 4-vector functions (e.g. boosting to CMS of the string) crashes with the “tachionic” complain.

18. String fusion algorithm to avoid too low or imaginary mass dq aq aq N There are 6 strings (3 cut cylinders): 3 x q-dq, 3 x aq-q q q q String fusion examples aq-q | aq-q | aq-q | q-dq | q-dq | aq-adq | aq-q | dq-adq | q-aq | adq-aq | adq-aq | adq-dq | q-aq | dq-q | aq-q | N1 q A dq q N2 dq aq Emergency flavor reduction: (s – anti-s)  (u/d – anti-u/d) (0) Emergency diquark reduction: (us – anti-d anti-s)  (u – anti-d) Emergency jump to 3-D CHIPS: (u – anti-d) + N  Quasmon

19. New CHIPS interaction cross-sections To avoid usage of the heavy HP package the neutron-nuclear CHIPS cross-sections have been improved for low energies (including (n,g) capture) There ENDF/B-VII data base was used for the cross-sections Inelastic cross-section is defined as sin=stot-sel The low energy 1/v cross-section is not implemented The cross-sections are parameterized for more than 100 isotopes The CHIPS inelastic cross-sections for pion-nuclear, kaon-nuclear, hyperon-nuclear and antiproton-nuclear interactions are calculated The CHIPS cross-sections are discussed in a special presentation A big mistake was found for Geant4 K+A interactions (= K-A ?!)

20. 105 nuclides covered by the present nA CHIPS implementation Ta-Cm Ag Only stable or long living isotopes (for A>227) with known natural abundance H-As

22. Not implemented

23. It means that the elastic nPb CHIPS cross-sections must be improved

24. Fit for the absorption contribution sabs/sin Only ENDF/B VII evaluation data are used R(p)=sabs/(stot-sel)=sabs/sin Approximation: R(p)=(p/B)-D+EXP[C-(p-M)2/W] (if R>1: R=1) The parameter “B” is a threshold of the non-absorption reaction Simulation The binary isotropic (n,g) reaction can be simulated rather fast Simulation of A(n,fission) reactions for A>225 is possible (?) The rest of inelastic reactions are simulated by CHIPS and the simulation is much slower than (n,g), but… at low energies a big part of the CHIPS simulation is quasi-elastic scattering on quasi-free nucleons and nuclear clusters, so the low energy simulation is expected to be fast enough.

25. sabs/sin

26. Conclusion • After the new CHIPS inelastic cross-sections are made for all particles, and the all-energies, all-projectiles nuclear fragmentation CHIPS model is debugged, the CHIPS physics list can be done • A bug (high inelastic cross-section for K+A interactions at very low energy) was found (LHEP/GEISHA) & corrected by the new CHIPS • The HP package, in some cases, can be replaced by the new low energy CHIPS nA processes • The last part of CHIPS to be implemented is the elastic scattering for pA, KA, HyperonA, anti-pA

27. Backup slides following